THREE CRUISES OF THE BLAKE 187 



earth can extend, and where the only changes are prob- 

 ably those of temperature, — animals living now in the 

 depths of the sea, under much the same conditions as 

 those which prevailed during the last days of the Juras- 

 sic period. 



" The conclusion drawn from these facts by Loven, 

 Moseley, Perrier, and others is that the abyssal fauna 

 has descended from the littoral and other shallow re- 

 gions, to be acclimatized at great depths. The conditions 

 of existence becoming more and more constant, or even 

 in the deeper regions perfectly uniform, species of the 

 most varied derivations, when they had once attained a 

 certain zone, could spread everywhere. This explains at 

 once how the deep-water fauna presents a very uniform 

 composition in all regions of the globe, but at the same 

 time includes various species the analogues of which live 

 in the sub-littoral regions of both cold and hot climates, 

 and may have sent an occasional wanderer into deeper 

 waters. 



" While the little dredging thus far done in deep 

 water has added to our knowledge a large number of 

 antique types which strongly remind us of Tertiary, 

 Cretaceous, and even of Jurassic forms, we should not 

 forget that such antique types occur everywhere, — in 

 limited numbers, it is true, — both in the shallower 

 regions of the sea and in fresh water. We can only 

 say that in the deep-water fauna a relatively larger 

 number of such antique forms has been found than else- 

 where." 



The final reports of the collections gathered in these 

 voyages were published by the specialists to whom they 

 were allotted, and appeared from time to time in the 



